Noninvasive blood flow measurement.

The difficulties involved in measuring blood flow in vivo have meant that this important clinical measurement has not, as yet, played a major role in the clinical management of patients. Recent developments in the use of noninvasive techniques have now remedied this situation. These techniques are calorimetry, thermography, plethysmography, ultrasound, and nuclear magnetic resonance. They can be subdivided into those techniques which measure volume flow in a limb, organ, or tissue bed and those which are vessel specific. Because of these developments, information is now available on normal blood flow values in specific blood vessels and this can now be used to study blood flow changes in a variety of pathological conditions.